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A review of The Hockey Stick and the Climate Wars: Dispatches from the Front Lines

by Michael E. Mann

(Columbia University Press, New York, 395 pp., 2012)

The topic of global climate change has become one of the hottest global issues for over a decade now, figuring prominently in U.S. politics, and leading to many international conferences on how to contain it. As a scientific debate, the facts were resolved over a decade ago. Survey after survey over the past decade have shown that roughly 95-99% of scientists who publish peer-reviewed research in climate change agree that global climate is changing rapidly and that humans are to blame. This is a level of consensus in science similar to that supporting gravity, plate tectonics, big bang cosmology, quantum physics—or evolution. Yet for reasons having nothing to do with science (i.e., religion or ideology), there are powerful vested interests in the United States that don’t like the “inconvenient truths” of evolution or big bang cosmology (creationists) or climate change (libertarians and free-market conservatives, backed by the fossil fuel industry). They are determined to fight scientific consensus by any means necessary. In contrast to Canada, or any major industrialized nation in Europe or in eastern Asia (including Japan, South Korea, China, and others), the U.S. is the only nation where science deniers (creationists and climate deniers) comprise any significant part of the population, and have a lot of influence in a major political party, so they can prevent any political action on the issue.

All of this is vividly described in Michael Mann’s book The Hockey Stick and the Climate Wars. Mann was the senior author on the famous “hockey stick” reconstructions of the past few centuries of climate, so called because a plot of changes in average temperature shows a steady linear trend over the centuries, then suddenly shoots upward in the past century. This gives the plot the shape of the blade of a hockey stick. The first part of Mann’s book describes his relatively quiet life as a graduate student in physics at Yale. He then switched to paleoclimate as a more interesting set of problems to focus on for his Ph.D. research, followed by a post-doc at the University of Massachusetts. During this time, he and his collaborators developed a technique for summarizing the dense record of climate change proxies from abundant tree rings with the sparser records from corals, ice cores, and lake sediments—and then connecting those to the past century of actual measured temperature records. As he carefully and clearly explains, you can’t just mix them all together, or the most abundant record (tree rings) will dominate the signal. He used a common multivariate statistical method, principal components analysis (PCA), so that each signal can be analyzed separately and then combined with equal weight. Mann then discusses how the original “hockey stick” plots of 1998 went back only 500 years into the past. As their data and methods were scrutinized and criticized by the scientific community, the proxy for climate got better, the error bars smaller, and the time range of the data began to reach back to over 1000 years ago. In addition, several other independent groups of researchers did their own analyses of the available data to check whether Mann et al. were right, and came up with a similar-looking “hockey stick” every time.

This is the way science is supposed to work: interesting or provocative new idea is proposed, but it must pass muster through peer-reviewers of a journal first. Once it is published, the idea will be criticized and scrutinized by the skeptical scientific community. If it has withstood all these criticisms and checks by qualified researchers, it becomes more broadly accepted. But as the second half of the book demonstrates, this is not the way it works in the public arena, especially in politics. Mann describes how the large edifice of conservative think-tanks and denier websites was set up to challenge the evidence of climate change, all bankrolled by money from oil and coal interests, and conservative foundations like the Scaife Foundation and the Koch brothers. These deniers began harassing climate scientists as far back as the early 1990s. When the Mann et al. (1998, 1999) “hockey stick” curve was published, he became their bête noire. The “hockey stick” was such a clear and powerful icon of the exceptional increase in temperature in the past century. Mann then describes the gut-wrenching stories of the major assault on science mounted by these deniers, a sordid story guaranteed to disgust anyone interested in science or truth. Through a handful of contrarians with strong ideological biases, there were many attempts to discredit the work of Mann and other climate scientists. As the author showed, most of these “scientists” simply don’t have a clue about what they’re doing, and made childish mistakes or misinterpretations of the data. These are easily pointed out in peer review, so they never pass muster and most of these papers end up published in the deniers’ house journals. The mistakes range from simple and stupid things (like not knowing that radiocarbon dates “B.P.” or “before present” means “before 1950”, or reading the data wrong) to more subtle things like McIntyre and McKitrick’s mistake of looking at the wrong principal component (which is weighted heavily on the yearly “noise”) instead of the PC that shows the long-term trend. Mann describes how contrarian Richard Lindzen of MIT is continually claiming he’s debunked global warming—but all he’s demonstrated is that he is good on focusing on factors that favor his biases toward cooling, but never looking at the feedback loops that tend to amplify warming.

By and large, though, the assault on Mann and other climate scientists doesn’t come from scientists playing by the rules. It comes from bloggers and right-wing media and political hacks whose sole job is to create “doubt” in the public mind, so that no progress can be made. They include Marc Murano, author of the “swiftboat” strategy against John Kerry in 2004, whose specialty was creating a smear campaign of lies to undermine the political standing of his opponents. These deniers range across a wide variety of other right-wingers who don’t care about unbiased scientific reality, but only blunting the understanding of the scientific consensus so a significant part of the American public is confused and uncertain. Mann describes the nasty slimeball tactics of these people in detail. He calls it the “Serengeti strategy”, where the predators pick off a vulnerable prey animal at the edge of the herd. In his case, the deniers don’t deal with the original data at all. Instead they persecute individual scientists with assaults on their character, lies about their science, huge demands for them to waste time and resources revealing every bit of data they have and every email they send, and even frequent death threats and envelopes of deadly toxins—all designed to intimidate and harass scientists in a given field who don’t want their lives, and the lives of their families, turned upside down. Fortunately, Mann has a strong character and the support of his fellow scientists, so he has apparently survived the worst of it. The latest attempt was the misguided attack by Virginia’s Attorney General Ken Cuccinelli, famous for his attempt to push various right-wing causes (including trying to cover the breast of the cartoon sketch of the goddess “Virtue” on the state seal). Cuccinelli tried to demand all of Mann’s records, data, and email while he was at University of Virginia on the grounds of fraud and misuse of grant funds (luckily, Mann has moved to Penn State, safely out of his reach). Just a few months ago, the courts rejected Cuccinelli’s fishing expedition to harass Mann, an event that occurred after the book went to press. Even more scary, Cuccinelli is the GOP candidate for Governor of Virginia, although his numerous blunders and extreme positions seem to have hurt his standing in the polls.

The book’s events finish in 2010, just after the GOP took over the House of Representatives and began their quixotic attempt to prevent climate change legislation from moving forward. Although it’s too early to declare this war over, it appears from recent polls that the nasty tactics and smear campaigns of the deniers have backfired. People are now realizing that the campaign against science was all about politics, with no real interest in respecting truth. Ironically, climate scientists keep reminding people that individual short-term weather events (such as heavy winter snows) are not the same as long-term changes that constitute climate. But the extraordinary heat waves and drought of the past few years, the record temperatures of 2009 and 2010, and especially Superstorm Sandy, have tilted the scales. A poll taken just after the 2012 election showed that 68% of Americans now regard climate change as a “serious problem,” up from only 48% in 2011, and 46% in 2009. A few weeks later, another poll found that 80% of Americans accept that climate is changing (compared to 73% in 2009), and 57% say the U.S. government should do something about it. And the most recent poll found that even a majority of GOP voters accept that climate change is real and that the government should do something about it (even if their leaders are still climate deniers)!

For anyone who wants an insider’s account of the climate wars, as well as a good description of how science works and is self-correcting (in contrast to the world of politics), this is an outstanding and riveting book. As a scientist who has published extensively in the fields of evolution and climate change, it scares the heck out of me that my family and I might be subjected to the same sort of harassment and intimidation and death threats. But it is encouraging that people like Mann stuck by their guns, and have withstood this pressure. It now appears that the attacks by ideologues no longer have the power to destroy careers that they once did. Now if we could only get the political will to face the reality, and work closely with the rest of the world (all of whom have accepted the truth) to mitigate the problem.

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34 Responses to “hockey brawls”

I have recently read both Michael Mann’s “The Hockey Stick and the Climate Wars” and Andrew Montfords “The Hockey Stick Illusion”. I don’t see how anyone who carefully reads both could not help but conclude that the hockey stick was bad science. “The Hockey Stick Illusion” is just full of serious, credible (even incredible) charges that I have not seen refuted. It does not in any way disprove AGW or even whether the hockey stick graph is true, but it does show that Mann’s poor quality analysis does not show it to be true. It also finds problems with other reconstructions.

The PCA is a particularly damning example. Mann used a centering convention that was previously unknown and did not disclose it. Without knowing this, there was no way for anyone to reproduce his results. McIntyre discovered this from a peice of FORTRAN code he found on an FTP site of Manns. The existance of this site was made known by reporter, David Appell in an article criticizing McIntyre. Email records show that this site was not disclosed in requests for data.

I’m familiar with Tamino’s review. If you haven’t read the book, it sounds very convincing, just like Judith Curry implies in comment 74. In comment 168, she provides a very good summary of what’s actually in the book.

One issue that Tamino ignores is statistical measures, which IMO deals the most devastating blow to Mann’s hockey stick.

Because of the prominence of Michael Mann’s work in the area, some of the lecture was devoted to the Hockey Stick, to the 2008 paper (the “upside down Tiljander” study to the initiated) and to Mann’s most recent area of focus, the influence of volcanoes on tree ring growth. Students learned that the Hockey Stick included a whole lot of inappropriate proxies and heard something of the issues with its verification statistics. The wallpapering of the Third Assessment with Mann’s magnum opus and John Houghton’s claims about unprecedented warmth based on this single study were described as “ridiculous”. “Ultimately a flawed study” was the conclusion, with a gory list of problems set out: inappropriate data, infilling of gaps, use of poorly replicated chronologies, flawed PC analysis, data and code withheld until prised from the grasp of the principals. In the paper’s defence, it was noted that it was an early attempt at a millennial reconstruction and that it did at least attempt to discern spatial variability, something that had not previously been done.

That was the gentle beginning. When we got onto Mann et al 2008, we learned about the silliness of the screening process, and students were invited to try screening a set of random generated time series in the way Mann had gone about this study.

Mann has since backed down a little on the twitter exchanges, deleting his ‘denier’ tweet, but still will brook no criticism:

…. a critical look at all of the northern hemispheric reconstructions of past temperature to date. It was not focussed entirely on Michael Mann’s work. I described each of the major studies and tried to highlight both their strengths and weaknesses – they all have some useful information but it is important to understand the limitations of the studies as well. Of course Mann’s work was mentioned as several of his papers have been so prominent over the last 15 years but I actually spent substantially more time taking apart the D’Arrigo et al. (2006) study on which I did much of the analysis.

This was a session where I wanted the students to critically look at the different studies and specifically address what we can learn from them and how the science can move on over the next decade. Such large scale reconstructions are critically important for understanding the controls on large climate variability, but as yet, due to great uncertainties and large differences in reconstructed amplitude, they are not yet very useful at constraining modelled estimates of future temperature change.

Bar some personal comments, much of what I said is published (see papers below) and is in the public domain.

Lastly, the “crock of xxxx” statement was focussed entirely on recent work By Michael Mann w.r.t. hypothesised missing rings in tree-ring records (a whole bunch of papers listed below). Although a rather flippant statement, I stand by it and Mann is well aware of my criticisms (privately and through the peer reviewed literature) of his recent work.

Paraphrasing Richard Feynman: Regardless of how many experts believe it or how many organizations concur, if it doesn’t agree with measurements, it’s wrong.

The time-integral of sunspot numbers (with appropriate proxy factor) calculates the average global temperature trend since 1610. This is shown at http://conenssti.blogspot.com/. An overlay of average global temperature measurements shows the oscillations above and below the trend that are the net effect of ocean cycles.

As with the original TAR series, these new records are not entirely independent reconstructions inasmuch as there are some predictors (most often tree ring data and particularly in the early centuries) that are common between them, but in general, they represent some expansion in the length and geographical coverage of the previously available data (Figures 6.10 and 6.11)

Tree growth is sensitive to temperature. Consequently, tree-ring width and tree-ring density, both indicators of tree growth, serve as useful proxies for temperature. ….. Comparisons with direct temperature measurements back to 1880 show a high correlation with tree growth. However, in high latitude sites, the correlation breaks down after 1960. At this point, while temperatures rise, tree-ring width shows a falling trend (a decline, if you will). This divergence between temperature and tree growth is called, imaginatively, the divergence problem.

The divergence problem has potentially significant implications for large-scale patterns of forest growth, the development of paleoclimatic reconstructions based on tree-ring records from northern forests, and the global carbon cycle. Herein we review the current literature published on the divergence problem to date, and assess its possible causes and implications. The causes, however, are not well understood and are difficult to test due to the existence of a number of covarying environmental factors that may potentially impact recent tree growth.

Can we construct ‘hockey stick’ climate charts from other (non -tree ring) proxies? Well, yes, but the individual plots shown only tend to go back to the year 1500 or so (ie, post MWP, although the combination published by Mann (Mann 2008)goes back 1300 years. (nice discussion in comments here too); http://www.skepticalscience.com/Hockey-stick-without-tree-rings.html

I’m not a scientist: not going to provide dualling links with cherry picked quotes, but who in their right mind doesn’t believe humans have really changed this planet? Look around you. Look at old maps and charts of an area and then at today’s maps and charts of the same place. Look at where forests and fields used to be. Or ice and glaciers. Look at all the garbage we produce. How about the invasive species that have been introduced by humans on purpose or accidentally (Asian Carp in the Great lakes comes to mind). Look at the crap floating in the Pacific following the 2011 earthquake and tsunami. Ever lived in a city that just keeps on growing? Ever notice the increase in pollution as a result? To fight so hard to keep the status quo (change nothing; we’re all OK here; climate change?–HA! Liberal hogwash [or worse, an international conspiracy http://www.ipcc.ch/) speaks volumes. I think most people are really afraid to admit that these changes are happening.

“I think most people are really afraid to admit that these changes are happening.”

Admission would then necessitate action and actions to arrest/reverse climate change can seem very daunting and frightening. Americans have been reluctant to embrace useful *simple* steps like mass-transit/car-pooling & recycling because they are inconvenient. And heaven forbid anyone be inconvenienced!

I live in New York City, and anywhere from five to ten times a year, my wife and I go to visit our in-laws that live in suburb 25 miles outside of Boston. When possible, I prefer to borrow a family member’s car to drive up there. Gas and tolls, the round trip is about $80.

Now, I could take Amtrak. If we did the Acela (which my wife prefers) that will cost us at least $400 round trip. The regular local Amtrak train is closer to $300 for the two of us.

So how about this, please send me a check for $220 (that’s an underestimate) everytime I visit my in-laws, and my wife and I will take the train, which will do virtually nothing for the environment. Of course, I’ll probably use those checks to spend on other frivolities that you don’t approve of, which requires carbon emissions, which are going to kill us all.

Mr B.
That is a good rant. I heartily agree with you.
Sure humans have changed and are changing the planet. And almost exclusively not for the better.

However, you are happy that the solution is “Do something! Anything! But do it now!!”?

Think about the simplicity of the great focus on carbon dioxide and the solutions provided. We have here a hugely complex problem (climate prediction) being pursued by a developing science, with solutions provided by theoretical economists and being hijacked by opportunistic politicians and predatory financiers.

I pride myself on being a practical and pragmatic person and have a great dislike of ‘feelgood’ gestures, and also of seeing things done simply because “thems the rules!”.

Mann describes the nasty slimeball tactics of these people in detail. He calls it the “Serengeti strategy”, where the predators pick off a vulnerable prey animal at the edge of the herd.

Isn’t science supposed to be like the Serengeti where weak ideas get picked off? McIntire and McKitrick found Mann’s methods to be weak and attacked them by publishing articles in peer reviewed journals.

If there is weakness in the science it certainly deserves to be picked apart. On both sides of the debate.

What worries me is the push that there only be one side to this particular debate.(“Because this time it is different! If we don’t act immediately it will be too late …. you just have to trust me on this, I know you have a science background, but I understand it better because I’m a politician”)

Very interesting review. The whole phenomenon of how ideology distorts reality–even to the point that trained people can’t do math when the correct answer conflicts with their worldview–is something that needs to be continually exposed, whether it issues from conservatives or liberals.

For example, replace “climate change” with “genetic modification,” and replace “right-wing foundation and Koch brothers” with “left-wing ideology and Greenpeace,” and you have a perfect mirror image of the phenomenon described in the review.

No, I’m not going to play dueling links, either. But canman, et al, as someone who is not a specialist in this field, tell me why I should believe a small handful of dissidents and reject the mainstream science? I have followed links before, and spent a long time digging out pertinent mainstream commentary, and they always turn out to be misrepresented or poor science.

Could you tell what other scientific fields you are more competent in than the professionals – genetics, particle physics, embryology, perhaps?

I find it a curious claim that whatever field a scientist is expert in in this matter – marine invertebrate biology, Arctic sea ice, Central American herpetology, paleoclimate, ocean chemistry, forest management, etc. they all are somehow painting the *same* wrong picture.

Kermit, I am not an expert in the various branches of climate science, but that does not stop me from being interested in them, learning more about them and forming opinions about them. I think all ideas in science can be summarized in increasing levels of detail, depending on how far someone wants to look into it. Some scientists are good at describing their work to a lay audience and so are some writers like Andrew Montford.

McIntyre is considered to be an expert in statistics. He saw Mann’s heavily promoted hockey stick and thought it looked like a stock market promotion. So he investigated it, found flaws and published his findings in peer reviewed journals and his blog. The Wegman panel of expert statisticians agreed with McIntyre’s results. I’ve been very unimpressed by the responses (or lack there of) of most climate scientists. I think it’s hypocritical of them to want us to trust their expertise on climate when they won’t trust expert statisticians.

Wegman’s group deserves severe criticism for their paraphrasing/editing, but Sinclair doesn’t go into the substance of Wegman’s report.

In the Deep Climate link(http://deepclimate.org/2010/11/16/replication-and-due-diligence-wegman-style/), DC admits that” M&M clearly identified a mistake (or, at best, a poor methodological choice)”. Then DC and his commenters get all excited about how varying a parameter in the generation of red noise can affect the hokeystickicity of the results of … Mann’s clearly identified mistake or poor methodological choice.

MIkeB, I’m sorry but I do not understand. Are you saying that Greenpeace has made billions selling genetically non-modified food globally and has now purchased politicians (via major campaign contributions), and allied with the mass media, have established a steady stream of propaganda to protect their empire? Also, where is the international consortium of scientists from multiple fields warning about the dangers of GMO? I’ve always had trouble with analogies, so I apologize if I’ve missed the obvious parallels.

A Landmark $19 billion award against the oil company in an Ecuadorean court was apparently the product of a criminal conspiracy.

Chevron got a court order for more than 500 hours of footage from “Crude” that never made it into the documentary.

……….show Donziger full of contempt for the country he says he cares about, openly boasting about how corrupt Ecuador’s judicial system is and planning to intimidate the judge because “the only language . . . this judge is going to understand is one of pressure, intimidation and humiliation.”

The filmmaker even recorded the lawyers lamenting that no pollution had spread from the original drilling sites and “right now all the reports are saying . . . nothing has spread anywhere at all” and how this lack of pollution was a serious problem.

But the footage also shows Donziger figuring he can brazen it out: “If we take our existing evidence on groundwater contamination, extrapolate based on nothing other than our . . . theory . . . then we can do it. And we can get money for it.”

Chevron will produce evidence that Donziger forged the signature of American experts on reports claiming widespread pollution — when these same experts had actually filed reports finding no such thing.

And that Donziger and his associates paid the Ecuadorean court’s “independent” expert more than a quarter of a million dollars so they could ghost-write his findings — the report that recommended the massive damages.

Chevron even promises to show that that Donziger offered a judge on the case a $500,000 bribe to swing the judgment.

But the real losers are the 30,000 Ecuadorean natives that Donziger claims to represent.
These are some of the poorest people on the planet, who’ve been told to expect a huge damage award. Worse, an eight-year campaign was apparently waged to convince them that they’re suffering mysterious illnesses, including cancer.

Maybe we can replace energy generated by coal and petroleum by burning the billions of strawmen that denialists,carbon apologists,and cynical billionaires with hearts of coal have blanketed the world with. ;)

“The whole phenomenon of how ideology distorts reality–even to the point that trained people can’t do math when the correct answer conflicts with their worldview–is something that needs to be continually exposed, whether it issues from conservatives or liberals.”

The anti-GMO movement is another example of ideology attempting to override scientific consensus.

MikeB- You would have a valid point if it had not been for this part of your comment:

“For example, replace “climate change” with “genetic modification,” and replace “right-wing foundation and Koch brothers” with “left-wing ideology and Greenpeace,” and you have a perfect mirror image of the phenomenon described in the review.”

The mistakes range from simple and stupid things (like not knowing that radiocarbon dates “B.P.” or “before present” means “before 1950”, or reading the data wrong) to more subtle things like McIntyre and McKitrick’s mistake of looking at the wrong principal component (which is weighted heavily on the yearly “noise”) instead of the PC that shows the long-term trend. mine] [emphasis mine]

Steve McIntyre graduated in pure mathematics at the University of Toronto and went on to study mathematical economics at MIT. He’s highly regarded in the field of statistics.

In principle component analysis, a data series is supposed to be centered, that is the mean of the series is subtracted from each member of the series so that it is left straddling the x axis. Mann subtracted the mean from only the 20th century. This is something which was previously unknown in PCA, which McIntyre and McKitrick dubbed “short centering”, and it is unambiguously wrong. In his book, Mann says it doesn’t matter which type of centering is used. Oh, Having the boundary of the centering period at the same place as the bend in the hockey stick doesn’t matter? McIntyre found that it overweighted 20th century hockey sticks. It weighted the hockey stick shaped “Sheep Mountain” over the shapeless “Mayberry Slough” by 390 times! He did 10,000 simulations using random red noise with tree ring properties and produced hockey sticks 99% of the time!

Mann will not admit that short centering is wrong. In fact he has the chutzpah to call it “modern centering” in his book. When reading a book by someone tooting his own horn, you should seek out alternate views for balance, especially for someone with Mann’s vindictiveness, whininess and reputation for selective disclosure.

From your link, this quote @1:37 PM from the question and answer discussion (and marked with a yellow smiley face) really stood out:

PaulM [Question 4:] Climate scientists seem to have invented a new statistic, the “RE” statistic, to replace the “R2″ statistic which is used by all other scientists and statisticians. What do you statisticians think of the “RE” statistic? Have you heard of it?

It never got an answer. According to Montford’s book, there are a number of computed values that are used to evaluate correlation. The most widely used and best understood one is called R2. The statistical literature recommends using a suite of different ones. The paleoclimate people have adopted a lesser used one called RE. Mann has refused to disclose his R2 results. Caspar Ammann, in his replication of Mann’s hockey stick had his R2 fail spectacularly. His RE also failed, albeit by a small margin. This is what he did to get his paper published:http://climateaudit.org/2008/08/08/caspar-ammann-texas-sharpshooter/
I’m waiting to see someone defend it. That horse looks like one hell of a longshot!

I would like to emphasize that there is nothing about Montford’s “Hockey Stick Illusion” that disproves AGW. It is an attack on the overhyping of AGW. Even without Climategate, Steve McIntyre’s results and the runaround he got should have been a story.

Did Mann deserve to be singled out for all the scrutiny that he got? He certainly benefited from his Hockey Stick papers. He was made a professor and got to be a lead author on the TAR. His graph also became an icon. When harsh climate mitigation efforts were proposed in the midst of a severe economic downturn, someone in Mann’s position is going to want his science to be squeaky clean, which it was not. The public was looking for a scapegoat. He partially has himself to blame. Despite what he says in his book, He was not completely exonerated. The NAS panel criticized his use of bristlecone pine’s and his short centering. Other inquiries criticized his lack of openness, especially with metadata. Politics can be a nasty business. Even McIntyre condemned the Cuccinelli probe. Mann has remained unrepentant and is now suing pundit Marc Steyn for what looks like editorial hyperbole.

There are proponents of AGW such as Richard Muller who are critics of Mann. These would include Tom Fuller and Steven Mosher, authors of the first climategate book, “Climategate: The Crutape Letters”. Mosher worked on Muller’s BEST project.